Electronic Component Module and Method for the Production Thereof

ABSTRACT

An electronic component module comprising: at least one multilayer ceramic circuit carrier ( 2, 3 ); at least one cooling device comprising at least one heat sink; a composite layer ( 5, 6 ) arranged at least in regions between the ceramic circuit carrier ( 2, 3 ) and the cooling device ( 4 ), said composite layer being formed for reactive connection to the ceramic circuit carrier ( 2, 3 ) during a primary process and for connection to the cooling device ( 4 ).

TECHNICAL FIELD

The invention relates to an electronic component module comprising atleast one multilayer circuit carrier and a cooling device comprising atleast one heat sink. Furthermore, the invention also relates to a methodfor producing an electronic component module of this type.

PRIOR ART

Electronic component modules comprising a plurality of multilayercircuit carriers are known. These are manufactured for example by LTCC(Low Temperature Cofired Ceramics), which represents a high-performancetechnology for producing ceramic circuit carriers from a plurality ofindividual layers. For this purpose, ceramic unsintered green films, forthe electrical plated-through, holes, are provided with openings bystamping-out, the openings are filled with electrically conductive pasteand the films are provided with planar line structures on their surfacein the screen printing method. A large number of these individual layerscan finally be laminated onto one another and sintered at a relativelylow temperature. The process yields multilayer buried layout structureswhich can be utilized for the integration of passive circuit elements.Moreover, it is thereby possible to create layout structures which havevery good radiofrequency properties, are hermetically sealed and havegood thermal stability.

With these properties, LTCC technology is suitable for applications inadverse surroundings, for example for sensors, in radiofrequencytechnology, for example in mobile radio and the field of radar, and inpower electronics, for example in vehicle electronics, transmission andengine control. Thermally demanding applications are often limited,however, by relatively poor thermal conductivity of the material, whichtypically has a thermal conductivity of 2 W/m K. For the cooling ofactive semiconductor components that are part of such LTCC modules ingeneral as surface mounted devices, merely mounting the LTCC substrateon a heat sink does not suffice. In particular, soldering or adhesivelybonding an LTCC substrate onto a heat sink, as is described in J.Schulz-Harder et al.: “Micro channel water cooled power modules”, pages1 to 6, PCIM 2000 Nürnberg, does not suffice.

An LTCC ceramic is compatible with silver metallization in the standardprocess. One conventional solution for LTCC substrates is therefore theintegration of thermal vias. These are vertical plated-through holeswhich are filled with silver-filled conductive paste and primarily servefor heat dissipation. An average thermal conductivity of 20 W/m K can beachieved in this way. In combination with silver-filled films, values of90 W/m K and 150 W/m K were made possible in the vertical and horizontaldirections, respectively. This is disclosed by M. A. Zampino et al.:“LTCC substrates with internal cooling channel and heat exchanger”,Proc. Internat. Symp. on Microelectronics 2003, Internat.Microelectronics and Packaging Society (IMAPS), 18-20 Nov. 2003, Boston,USA.

A further solution is the mounting of semiconductor ICs (integratedcircuits) having a high heat loss, for example power amplifiers, incutouts of the LTCC circuit board directly on the heat sink.

Furthermore, solutions are known what are based on the integration ofliquid-filled channels. In this case, the cooling is effected byconvection of a liquid having a high heat capacity, for example water,as is described in the abovementioned prior art in accordance with J.Schulz-Harder et al.: “Micro channel water cooled power modules”, andfurthermore in M. A. Zampino et al.: “Embedded heat pipes with MCM-CTechnology”, Proc. NEPCON West 1998 Conference Vol. 2, Reed ExhibitionNorwalk, Conn. USA 1998, pages 777-785, Vol. 2, (Conf. Anaheim, USA, 1-5Mar. 1998).

A solution based thereon does not utilize the heat capacity of thecooling liquid for the heat transfer, but rather the latent heat of aphase transition. This is described in the abovementioned prior art inaccordance with M. A. Zampino et al.: “LTCC substrates with internalcooling channel and heat exchanger” and in W. K. Jones et al.: “Thermalmanagement in low temperature cofire ceramic (LTCC) using high densitythermal vias and micro heat pipes/spreaders”, Proc. Internat. Symp. onMicroelectronics 2002, Internat. Microelectronics and Packaging Society(IMAPS), 10-13 Mar. 2002, Reno, USA. The “heat pipes” explained thereinare used according to the prior art for example for the cooling ofprocessors in compact computers such as laptops, for example.

Besides these methods suitable for LTCC, for highly sintering aluminumoxide ceramic the so-called direct copper bonding process is suitableand widespread for connecting circuit carriers composed of sinteredaluminum oxide directly to cooling films composed of copper atapproximately 1100° C. This is described in J. Schulz-Harder et al.:“Micro channel water cooled power modules” and J. Schulz-Harder et al.:“DBC substrate with integrated flat heat pipe”, EMPC 2005, The 15thEuropean Microelectronics and Packaging Conference Exhibition, 12-15Jun. 2005, Bruges, Belgium.

SUMMARY OF THE INVENTION

The invention is based on the object of providing an electroniccomponent module and a method for producing an electronic componentmodule of this type wherein highly thermally conductive substrates canbe stably connected to a multilayer circuit carrier in a simple mannerand with little outlay and the heat dissipation can be improved.

This object is achieved by means of an electronic component modulehaving the features according to patent claim 1, and a method having thefeatures according to patent claim 12.

An electronic component module according to the invention comprises atleast one multilayer ceramic circuit carrier and a cooling devicecomprising at least one heat sink. At least one composite layer isarranged at least in regions between the ceramic circuit carrier and thecooling device, said at least one composite layer being formed forreactive connection, in particular for LTCC-reactive connection, to theceramic circuit carrier during a primary process and for connection tothe cooling device. By means of said composite layer and in particularthe configuration thereof, it is possible to achieve a stable connectionbetween the components of the component module. Furthermore, thecomposite layer can be produced with little outlay since it combinesreactively with the ceramic circuit carrier. Consequently, theconnection of the circuit carrier to said composite layer can beproduced automatically in particular during the actual process ofjoining together the ceramic circuit carrier with the cooling device.Owing to its material embodiment, the composite layer can be reactivelyconnected to the circuit carrier stably during a primary process. Aprimary process is understood to mean a process which is carried outprimarily for a different bond production between components of thecomponent module. In particular, this bond can be reactively producedautomatically in an LTCC process. A separate downstream method step suchas is the case as a result of non-reactive connection such as withsoldering or adhesive bonding no longer has to be carried out here.Consequently, reactive connection is understood to mean all processeswhich produce a dual effect. Firstly the primary effect as a result ofthe process and secondly the connection of the composite layer to thecircuit carrier. In a preferred LTCC process, the dual effect isafforded by the fact that firstly the individual layers of the circuitcarrier can be connected and, in addition, according to the invention,the reactive bond between the composite layer and the circuit carriercan be formed.

Particularly when the circuit carrier is formed as an LTCC circuitcarrier, the composite layer is formed as a reactive coating suitablefor LTCC. In this configuration, what can then also be achieved in theactual LTCC process is that the ceramic circuit carrier is automaticallyconnected to the composite layer in a mechanically stable manner.Furthermore, the mechanically stable connection to the cooling device isalso ensured.

Consequently, the reactive connection can be effected under thecustomary process conditions in an LTCC process for applying the circuitcarrier to the cooling device.

Preferably, the composite layer is formed over the whole area betweenthe circuit carrier and the cooling device. This enables a particularlyeffective fixing and furthermore also an optimum heat dissipation.

Preferably, the cooling device is formed for lateral heat dissipationand the heat sink extends laterally beyond the dimensions of the circuitcarrier at least at one side. The lateral cooling concept makes itpossible to form a more compact electronic component module whichnevertheless enables an improved heat dissipation.

It is particularly preferred if the circuit carrier is formed as aceramic LTCC circuit carrier and the composite layer, for reactivelyproducing a bond with the circuit carrier, is formed or can be producedduring the LTCC process for forming the ceramic circuit carrier. Whatcan be achieved by this configuration is that the connection can beproduced automatically in practice during the LTCC method wherein theindividual layers are laminated onto one another and are sintered at acorresponding temperature. Consequently, as an essential advantage overthe prior art, the connection does not have to be produced in a furthermanufacturing method downstream of the LTCC process, for example bymeans of hard soldering, rather said connection can be effectedessentially simultaneously with, or overlapping at least at times, theconnecting production of the individual layers of the circuit carrier.

The composite layer is preferably formed at least as a monolayer,component-free and electrically line-free LTCC film. In thisconfiguration, the composite layer is therefore provided as anintermediate film. In particular, it can then be provided that thecomposite layer with an in particular individual intermediate film isfitted in a sintering process under adapted conditions, in particularconcerning the gas atmosphere and the temperature profile. Inparticular, provision is made here for applying said intermediate filmto the cooling device.

The composite layer can also be formed at least proportionally fromglass.

It can likewise be provided that the composite layer is formed at leastproportionally from nanocrystalline material, in particularnanocrystalline aluminum oxide. It can likewise be provided that thecomposite layer is formed at least proportionally from a ceramicmaterial, in particular silicon oxide and/or silicon nitride.

The composite layer can be formed at least proportionally from areactive metal, in particular from titanium.

It proves to be particularly preferred if the bond between the circuitcarrier and the composite layer is formed by a sintering process at atemperature of between 840° C. and 930° C., in particular atapproximately 900° C. With these process conditions it is also possibleto ensure an optimum formation of the ceramic circuit carrier and inparticular the bond between the individual layers. At the same time, thereactive bond between the composite layer and the circuit carrier canalso be made possible with these optimized process conditions.

In a method according to the invention for producing an electroniccomponent module, at least one ceramic multilayer circuit carrier isconnected to at least one cooling device comprising at least one heatsink. A composite layer for connecting the components is formed at leastin regions between the ceramic circuit carrier and the cooling device.The composite layer is reactively connected to the circuit carrierduring the process of connecting the individual layers of the circuitcarrier. This production method can provide a significantly improvedcomposite structure which can be realized with significantly less outlayin terms of production engineering.

It proves to be particularly preferred if the circuit carrier is formedas a ceramic LTCC circuit carrier and the composite layer is connectedto the circuit carrier during the LTCC process. The heat sink-ceramiccomposite can thereby be obtained at relatively low temperatures, thecooling device preferably being provided with a reactive composite layersuitable for LTCC in an upstream process step for the configuration ofthe electronic component module. Afterward, the LTCC multilayer andhence the LTCC circuit carrier is then applied to the prepared surface,in particular by sintering, under corresponding process conditions.

Advantageously, at least one monolayer, component-free and line-free(without electrical lines) and also electrically insulating LTCC film asan intermediate film in the form of a gradient film is formed as thecomposite layer. In this case, it is preferably provided that theintermediate film is applied in a sintering process under adaptedconditions. In this case, it can be provided that this is effected undera nitrogen atmosphere with addition of argon. This procedure enables theprocess parameters to be adapted, for example in order to obtain anoptimum metal-ceramic composite, without consideration of the standardconditions for the connection of the individual layers of the circuitcarrier, and in particular the standard conditions of LTCC technology.These standard conditions of LTCC technology are determined by thepresence of line structures composed of silver-containing screenprinting paste. In particular, the gas atmosphere is in this casecharacterized by oxygen or air.

The functional LTCC films of the multilayer circuit carrier which haveelectronic devices and integrated line structures are laminated onto theintermediate film. In order to avoid the xy shrinkage of the functionallayers, it is preferably the case that in addition a sacrificial filmcomposed of aluminum oxide (Al₂O₃) is laminated onto the top side of thecircuit carrier and finally sintered in the so-called zero-shrinkagemethod.

Furthermore, it can be provided that the composite layer is formed atleast proportionally from glass, is applied in particular by screenprinting and is subsequently thermally treated. This configuration alsoenables an optimum composite structure during the process of connectingthe individual layers of the circuit carrier.

It can also be provided that the composite layer is applied at leastproportionally from nanocrystalline material, in particular is appliedby a screen printing method. Nanocrystalline aluminum oxide, inparticular, is provided as the nanocrystalline material. Since thesintering temperature decreases as the grain size decreases,nanocrystalline material opens up an LTCC-compatible process path.

Furthermore, the composite layer can also be formed at leastproportionally from a ceramic material, in particular from silicon oxideand/or silicon nitride. In this configuration, it can be provided thatsaid ceramic material is applied by a sputtering method, in particularis sputtered onto the cooling device. The ceramic layers deposited byphysical low-temperature methods serve as adhesion layers for the LTCCceramic applied later.

Furthermore, the composite layer can also be formed at leastproportionally by a coating with reactive metals, in particulartitanium. These reactive metals should be regarded as outstandingadhesion promoters for metal contacts.

The composite layer can also be formed at least proportionally byreactive ion beam etching with oxygen. The ion bombardment gives rise toan intermixing of the metal surface which leads to a graded metal-oxidetransition. Prior sputtering, for example of silicon, gives rise forexample to a graded metal-metal oxide-silicon oxide transition as abasis for the composite with the LTCC ceramic.

Preferably, the ceramic circuit carrier and the composite layer areconnected to one another by sintering at a temperature of between 840°C. and 930° C., in particular at approximately 900° C.

The invention therefore proposes process engineering solutions for theintegration of highly thermally conductive heat sinks in LTCC. Thecooling device and the heat sink can have any desired form, inprinciple, for the production process proposed. The configuration as alaterally extended shaped body having a homogeneous thickness isadvantageous, however. Said shaped body can be areally smaller, largeror congruent with the multilayer ceramic circuit carrier. A metallicelement can preferably be provided for the heat sink of the coolingdevice. In particular, the heat sink can be formed from copper, whichhas a very high thermal conductivity of approximately 400 W/m K. Othermetals having adapted coefficients of thermal expansion are alsopossible, however, depending on the thickness ratio of the multilayercircuit carrier to the heat sink. By way of example, it is also possibleto use copper-molybdenum composite metals having thermal conductivitiesin the region of approximately 200 W/m K. In order to compensate forslightly different expansion coefficients, the LTCC ceramic can beapplied with the same thickness on both sides of the heat sink.

The method according to the invention proves to be particularlyadvantageous when the intention is to produce an electronic componentmodule having at least two multilayer circuit carriers and a pluralityand hence at least two integrated heat sinks. Particularly in the caseof a multilayer system of this type it is particularly difficult to beable to ensure a sufficient composite structure by means of conventionaltechnology. In particular by means of the method according to theinvention it is also possible to produce such a multilayer systemrelatively simply and with little outlay and in particular to enable aplurality of heat sinks to be formed integrally. For precisely in thecase of such complex structures, the bond between the circuit carriersand the composite layers and therefore also the heat sinks can be madepossible automatically during the lamination and sintering of theindividual layers of these circuit carriers. Consequently, it is nolonger necessary to carry out respectively separate fitting, for exampleby soldering or adhesive bonding, in a complicated and cost-intensivemanner after said production of the ceramic circuit carriers. In thecase of integrated heat sinks, in particular, the method according tothe invention can enable production to be considerably facilitated.

Furthermore, in the case of the electronic component module according tothe invention, it is possible to achieve a purely passive heatdissipation without mobile substances, phase boundaries or phasetransitions. Furthermore, a considerable increase in the thermalconductivity is possible. By way of example, this can be achieved byapproximately ten-fold by comparison with thermal vias with the use ofcopper-molybdenum-copper laminates. A further increase in the thermalconductivity to up to 400 W/m K or higher can be made possible with theuse of pure copper substrates or composite materials, for example on thebasis of carbon nano fibers.

In addition to a high thermal conductivity, it is also possible toenable a stable material composite by means of alternating layers ofelectrical functional ceramic (ceramic circuit carriers) and highlythermally conductive material. Particularly when a heat sink is formedwith laterally larger dimensions than a circuit carrier, it is alsopossible to enable simple mounting by means of screws in the region ofthe projecting heat sink.

Simple further processing by complete population of the module and adefined interface with the surroundings can likewise be achieved. In thecase of a ceramic individual layer of the composite layer, a highelectrical insulation in conjunction with high thermal coupling isachieved. Last but not least it is also possible to enable efficientheat dissipation from buried devices in the circuit carrier structure,in particular the LTCC ceramic.

BRIEF DESCRIPTION OF THE DRAWING

Exemplary embodiments of the invention are explained in more detailbelow with reference to a schematic drawing. The single FIGURE shows asectional illustration through an electronic component module accordingto the invention in accordance with an exemplary embodiment.

The electronic component module 1 comprises a first multilayer ceramicLTCC circuit carrier 2 and a second multilayer ceramic LTCC circuitcarrier 3. These two circuit carriers 2 and 3 are arranged on oppositesides of a heat sink 4 assigned to a cooling device. In the exemplaryembodiment, the heat sink 4 is therefore arranged integrally in theelectronic component module 1 between the two circuit carriers 2 and 3.The heat sink 4 extends beyond the dimensions of the LTCC circuitcarriers 2 and 3 on both sides in a lateral direction (x direction).Furthermore, holes 41 and 42 are formed in the heat sink 4, which areprovided for fixing, in particular screwing, to further components or ahousing.

A first composite layer 5 is formed between the upper LTCC circuitcarrier 2 and the heat sink 4, which is formed from copper in theexemplary embodiment, said first composite layer connecting said firstcircuit carrier 2 to the heat sink 4 in a mechanically stable manner. Acomposite layer 6 is likewise formed in a corresponding manner betweenthe heat sink 4 and the second LTCC circuit carrier 3. Both compositelayers 5 and 6 are formed for reactive connection to the ceramic LTCCcircuit carriers 2 and 3. This means that the bond between the compositelayer 5 and the first circuit carrier 2 and the bond between the secondcomposite layer 6 and the second circuit carrier 3 are also formedduring the LTCC process for connecting the respective individual layersof the circuit carriers 2 and 3.

In the exemplary embodiment, the composite layers 5 and 6 are in eachcase formed over the whole area between the heat sink 4 and therespective circuit carrier 2 and 3. Furthermore, said composite layers 5and 6 extend essentially over the entire surface of the heat sink 4 in alateral direction. It can also be provided that the composite layers 5and 6 are in each case formed only in regions. In particular, thecomposite layers 5 and 6 are formed at those locations at which thegreatest amount of heat is generated on account of the arrangement ofelectronic devices in the respective circuit carriers 2 and 3. As aresult of such targeted local formation of the composite layers 5 and 6,heat can then also be transported away in the best possible manner. Heatis transported away in this manner laterally in the exemplary embodimentshown.

The electronic component module 1 shown in the FIGURE is produced insuch a way that firstly the composite layers 5 and are applied to theheat sink 4 on both sides. Various configurations can be provideddepending on how said composite layers are intended to be formed. Theseconfigurations are mentioned in the general part of the description. Inprinciple, any desired combination of the various embodiments of acomposite layer mentioned there can also be provided.

After said composite layers 5 and 6 have been applied on the heat sink4, the multilayer circuit carriers 2 and 3 are subsequently formed in anLTCC method. At the same time, during this method, in which theindividual layers of the circuit carriers 2 and 3 are laminated onto oneanother and then sintered at a temperature of approximately 900° C., thebond between the composite layer 5 and the circuit carrier 2, on the onehand, and the composite layer 6 and the second circuit carrier 3, on theother hand, is also formed reactively.

With the completion of the circuit carriers 2 and 3 by means of the LTCCprocess, the complete electronic component module 1 and in particularthe bond between the composite layers 5 and 6 and the circuit carriers 2and 3, respectively, are also already formed completely according to theinvention.

1. An electronic component module comprising: at least one multilayerceramic circuit carrier; at least one cooling device comprising at leastone heat sink; and a composite layer arranged at least in regionsbetween the ceramic circuit carrier and the cooling device, saidcomposite layer being formed for reactive connection to the ceramiccircuit carrier during a primary process and for connection to thecooling device.
 2. The electronic component module as claimed in claim1, wherein the composite layer is formed over the whole area between thecircuit carrier and the cooling device.
 3. The electronic componentmodule as claimed in claim 1, wherein the cooling device is formed forlateral heat dissipation and the heat sink extends laterally beyond thedimensions of the circuit carrier at least at one side.
 4. Theelectronic component module as claimed in claim 1, wherein the primaryprocess is an LTCC process for connecting the individual layers of theceramic circuit carrier.
 5. The electronic component module as claimedclaim 1, wherein the composite layer is formed at least as a monolayer,component-free and line-free LTCC film.
 6. The electronic componentmodule as claimed in claim 1, wherein the composite layer is formed atleast proportionally from glass.
 7. The electronic component module asclaimed claim 1, wherein the composite layer is formed at leastproportionally from nanocrystalline material.
 8. The electroniccomponent module as claimed claim 1, wherein the composite layer isformed at least proportionally from ceramic material.
 9. The electroniccomponent module as claimed in claim 1, wherein the composite layer isformed at least proportionally from a reactive metal.
 10. The electroniccomponent module as claimed in claim 1, wherein the bond between thecircuit carrier and the composite layer is formed by a sintering processat a temperature of between 840° C. and 930° C.
 11. The electroniccomponent module as claimed in claim 1, wherein at least one coolingdevice is formed integrally between two multilayer circuit carriers. 12.A method for producing an electronic component module comprising:connecting at least one ceramic multilayer circuit carrier to a coolingdevice comprising at least one heat sink; and, forming a composite layerfor connecting the at least one ceramic multilayer circuit carrier tothe cooling device at least in regions between the ceramic circuitcarrier and the cooling device, the composite layer being reactivelyconnected to the circuit carrier during a primary process.
 13. Themethod as claimed in claim 12, the circuit carrier is formed as aceramic LTCC circuit carrier and the composite layer is connected to thecircuit carrier during an LTCC process as the primary process.
 14. Themethod as claimed in claim 12, wherein, the composite layer is formedprior to the formation of the multilayer circuit carrier on the coolingdevice.
 15. The method as claimed in claim 12, wherein at least onemonolayer, component-free and line-free LTCC film is formed as thecomposite layer.
 16. The method as claimed in claim 12, wherein thecomposite layer is formed at least proportionally from glass, is appliedin particular by screen printing and is subsequently thermally treated.17. The method as claimed in claim 12, wherein, the composite layer isformed at least proportionally from nanocrystalline material, and isapplied in particular by screen printing.
 18. The method as claimed inclaim 12, wherein the composite layer is formed at least proportionallyfrom a ceramic material, and is applied by sputtering in alow-temperature method.
 19. The method as claimed in claim 12, whereinthe composite layer is formed at least proportionally by a coating withreactive metals.
 20. The method as claimed in claim 12, wherein thecomposite layer is produced at least proportionally by reactive ion beametching with oxygen of the metallically formed heat sink.
 21. The methodas claimed in claim 20, wherein silicon is applied by sputtering priorto the ion beam etching.
 22. The method as claimed in claim 12, whereinthe circuit carrier and the composite layer are connected by sinteringat a temperature of between 840° C. and 930° C.